The present invention relates to a plasticized sulfur composition, which composition is useful for coating walls or other surfaces to form an acid- or corrosion-resistant surface which is resistant to cracking upon exposure to fluctuating temperatures.
Plasticized sulfur mixtures are disclosed in various references. For example, J. I. Jin gives the following tabular comparison of plasticized sulfur compositions in his report given at the ACS Los Angeles meeting, Symposium on New Sulfur Chemistry, Apr. 19, 1974, page 235:
TABLE I ______________________________________ COMPARISON OF PLASTICIZED SULFUR COMPOSITIONS Melt Plasticizer Viscosity Regulator Reference ______________________________________ Mixture of dithio Chlorinated and higher thiols Polyphenyls (2) Arylenepolysulfide (ZM-399)* and aliphatic poly- sulfide (LP-3)** None (3,6) ##STR1## Diphenyl dithiophosphate (4) and styrene Dithiol Monomercaptan (5) ______________________________________ *Thiokol's styrene polysulfide **Thiokol's liquid polysulfide (2) Louthan, R. P., U.S. Pat. No. 3,434,852 (March 1969). (3) Barnes, M. D., U.S. Pat. No. 3,316,115 (April 1967). (4) Signouret, J. B., U.S. Pat. No. 3,560,451 (February 1971). (5) Kane, J. C., U.S. Pat. No. 3,447,941 (June 1969). (6) Dale, J. M., Report No. 1 (Sept. 1961); Report No. 2 (April 1962); Report No. 3 (June 1963), Project 10922, Southwest Research Institute.
In "New Uses of Sulfur", James R. West, Editor, Advances in Chemistry Series 140, ACS, Washington, D.C., 1975, B. R. Currell et al describe various sulfur plasticizers in their report tilted "Plasticization of Sulfur". The report gives a study of the chemical interaction of additives (such as polymeric polysulfides, unsaturated hydrocarbons and phenolic derivatives) with sulfur and also measurement, using differential scanning calorimetry and electron microscopy, of the rate of crystallization of sulfur in the presence of these additives. Limonene, myrcene, dicyclopentadiene and cycloocta-1,3-diene were found particularly effective in retarding sulfur crystallization.
British Pat. No. 1,182,171 describes plasticization of sulfur using a dithio polysulfide, an olefin polymer, and an ethylenically unsaturated compound wherein the above constituents are heated and mixed with sulfur at a temperature between 100.degree. and 200.degree. C. to form a homogeneous plastic. The dithio polysulfide used was of the formula ##STR2## The dithio polysulfide was referred to in the British patent as an Rs resin.
The British patent teaches that the dithio compound is necessary in order to secure reaction of the olefin polymer and the ethylenically unsaturated compound with the sulfur. Thus, the British patent states on page 2:
"The use of the resin R.sub.s is thus necessary for the reaction with the olefine polymer and optionally a monomeric ethylenically unsaturated compound."
U.S. Pat. No. 3,465,064 discloses a plasticized sulfur reported to have good adhesion to various surfaces, which plasticized sulfur is prepared by incorporating into molten sulfur a polythiomethylene alkanol, an olefin polymer and optionally an ethylenic compound, and in heating the material thus obtained until there is formation of a homogeneous and plastic composition.
The use of phosphorus sulfide, in particular P.sub.2 S.sub.5, has been disclosed as a sulfur plasticizer. See, for example, U.S. Pat. No. 3,935,352 to W. G. Toland. U.S. Pat. No. 3,459,717 also discloses the use of a diester of dithiphosphoric acid in plasticization of sulfur, and the diester is prepared by reacting an alcohol or phenol with P.sub.2 P.sub.5. One classic reference book [Beat Meyer, ed., Elemental Sulfur (Intescience Publishers, New York, 1965) p. 359] gives modifiers that tend to make sulfur rubbery, then states that in contrast phsophorus "produces such extensive crosslinking that only a glassy material is produced."
U.S. Pat. No. 3,453,125 is directed to a method of reducing the viscosity of plasticized sulfur compositions by forming a mixture of plasticized sulfur with a persulfide compound. The persulfide additive can be prepared by the reaction of elemental sulfur with a mercapto compound selected from mercapto acids, mercapto alcohols, etc.
Materials for plasticizing the sulfur according to U.S. Pat. No. 3,453,125 include ". . . aryl polysulfides, alkyl polysulfides, organic polythiols, chlorinated polyphenyls, wood rosin, natural rubber, butyl rubber, olive oil, organic esters, alkyl resins, and the like, and combinations of these. Particularly applicable are the sulfur compositions plasticized by organic polythiols."
The use of mica in plasticized sulfur compositions is disclosed in commonly assigned U.S. Pat. No. 4,026,719. Plasticizers disclosed in U.S. Pat. No. 4,026,719 include inorganic materials such as iron, arsenic, and phosphorus sulfides, but the particularly preferred plasticizers are stated to be organic compounds.